1. Field of the Invention
The present invention relates to a sheet post-processing apparatus that performs post-processing such as stapling sheets on which images are formed in an image forming main body, and an image forming apparatus including the image forming main body and the sheet post-processing apparatus.
2. Related Art
Conventionally, a sheet post-processing apparatus has been used, which performs post-processing on a sheet (or a stack of sheets) on which an image is formed in an image forming main body such as a copy machine, a multi-functional device and the like. The sheet post-processing apparatus is disposed adjacently to the image forming main body. As the post-processing, punching processing on a sheet, staple processing on s stack of sheets, and double- and triple-fold processing on a sheet (a stack of sheets) are exemplified.
Tilted end-binding processing is one example of the staple processing. Tilted end-binding is a process for driving a staple into sheets in a vicinity of a corner of the sheets while the staple is tilted with respect to a direction of conveyance of a sheet. Sheet post-processing apparatuses capable of tilted end-binding processes are equipped with a stapling unit that staples a stack of sheets that is obtained through stack processing performed for a plurality of sheets, a movable table that is rectilinearly movable in unison with the stapling unit in a perpendicular direction perpendicular to a direction of conveyance of a sheet, a rectilinearly driving portion that rectilinearly moves the movable table in the perpendicular direction, and a rotationally driving portion that tilts the movable table so that the stapling unit tilts to a staple-driving position to drive a staple at an angle with respect to the direction of the conveyance of a sheet.
With this kind of sheet post-processing apparatus, the rectilinearly driving portion rectilinearly moves the stapling unit via the movable table and the rotationally driving portion rotates the stapling unit via the movable table. In this manner, the sheet post-processing apparatus implements the tilted edge-binding process by driving the staple near a corner of sheets while the staple is tilted with respect to the direction of the conveyance of a sheet.
It is necessary for the sheet post-processing apparatuses capable of the tilted edge-binding process to maintain the stapling unit tilted. For example, a setup to maintain a stapling unit tilted has been considered. It employs a rotationally driving portion with a motor for rotating a movable table so as to tilt a stapling unit and a locking mechanism to electrically lock the rotation of the motor.